Support FilePaths instead of raw strings in XML code.

PiperOrigin-RevId: 655177026
Change-Id: I55b055551384b01ba7a4baa5d75fbe3329b7d25d

src/xml/xml_api.cc

@@ -37,6 +37,8 @@
 
 //---------------------------------- Globals -------------------------------------------------------
 
+namespace {
+
 // global user model class
 class GlobalModel {
  public:
@@ -61,7 +63,7 @@ std::optional<std::string> GlobalModel::ToXML(const mjModel* m, char* error,
     return std::nullopt;
   }
   mj_copyBack(spec_, m);
-  std::string result = mjWriteXML(spec_, error, error_sz);
+  std::string result = WriteXML(spec_, error, error_sz);
   if (result.empty()) {
     return std::nullopt;
   }
@@ -86,6 +88,8 @@ GlobalModel& GetGlobalModel() {
   return global_model;
 }
 
+}  // namespace
+
 //---------------------------------- Functions -----------------------------------------------------
 
 // parse XML file in MJCF or URDF format, compile it, return low-level model
@@ -96,7 +100,7 @@ mjModel* mj_loadXML(const char* filename, const mjVFS* vfs,
 
   // parse new model
   std::unique_ptr<mjSpec, std::function<void(mjSpec*)>> spec(
-      mjParseXML(filename, vfs, error, error_sz),
+      ParseXML(filename, vfs, error, error_sz),
       [](mjSpec* s) { mj_deleteSpec(s); });
   if (!spec) {
     return nullptr;
@@ -211,7 +215,7 @@ mjModel* mj_loadModel(const char* filename, const mjVFS* vfs) {
 
 // parse spec from file
 mjSpec* mj_parseXML(const char* filename, const mjVFS* vfs, char* error, int error_sz) {
-  return mjParseXML(filename, vfs, error, error_sz);
+  return ParseXML(filename, vfs, error, error_sz);
 }
 
 
@@ -225,7 +229,7 @@ mjSpec* mj_parseXMLString(const char* xml, const mjVFS* vfs, char* error, int er
 
 // save spec to XML file, return 1 on success, 0 otherwise
 int mj_saveXML(const mjSpec* s, const char* filename, char* error, int error_sz) {
-  std::string result = mjWriteXML(s, error, error_sz);
+  std::string result = WriteXML(s, error, error_sz);
   if (result.empty()) {
     return 0;
   }
@@ -241,7 +245,7 @@ int mj_saveXML(const mjSpec* s, const char* filename, char* error, int error_sz)
 
 // save spec to string, return 1 on success, 0 otherwise
 int mj_saveXMLString(const mjSpec* s, char* xml, int xml_sz, char* error, int error_sz) {
-  std::string result = mjWriteXML(s, error, error_sz);
+  std::string result = WriteXML(s, error, error_sz);
   if (result.size() >= xml_sz) {
     std::string error_msg = "Output string too short, should be at least " +
                             std::to_string(result.size()+1);